Hybrid electric vehicles (HEVs) typically include an alternating current (AC) electric motor driven by a direct current (DC) power source, such as a battery. Stator windings of the electric motor may be coupled to a power inverter module that performs a rapid switching function to convert the DC power to AC power to drive the electric motor, which in turn drives a drivetrain shaft of the HEV.
The temperature of motor stator windings is an important parameter and may be used for a variety of purposes. For example, stator winding temperatures may be an input in various motor control algorithms, particularly algorithms that utilize stator resistance as a control variable. Additionally, stator winding temperatures can also be used to detect high motor temperatures to prevent overheating. Conventionally, the temperatures of the stator windings are measured by a temperature measurement sensor, such as a thermistor or thermocouple, installed or mounted on one of the stator windings. However, in some systems, there may be large temperature gradients between the temperature sensor and the high temperature areas of the stator winding, which may result in accuracy issues. More than one sensor may be used, although each additional sensor raises issues with placement, cost, reliability, service, and maintenance.
To reduce or even eliminate the need for temperature sensors, sensorless stator winding temperature estimation techniques have also been developed. These temperature estimation techniques may employ complex motor thermal models based on machine geometry and thermal and electrical properties. However, in many cases, information regarding such motor geometry or thermal or electrical properties may not be readily available, and the resulting assumptions may result in inaccuracies. Other sensorless stator winding temperature estimation techniques have been developed that work well for zero or low speed temperature estimation (e.g., below 75 rpm); however, these techniques may not yield accurate results at higher motor speeds.
Accordingly, it is desirable to provide methods and systems for estimating stator winding temperatures over the entire motor speed operating range (i.e., low operating speeds and high operating speeds) with improved accuracy. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.